This document defines myocardial infarction and provides epidemiological data. It begins by defining myocardial infarction as the irreversible necrosis of heart muscle due to prolonged ischemia resulting from a blockage in a coronary artery. It then notes that over 735,000 Americans have heart attacks each year. Risk factors include increasing age, male sex, hypertension, dyslipidemia, diabetes, smoking, obesity, physical inactivity, and excessive alcohol consumption. The pathophysiology involves rupture of an atheromatous plaque leading to thrombus formation and coronary artery occlusion, causing ischemia and eventual cell death.